Art of cracking hydrocarbon oils



July'23 1929. E.-w. lsoM ART OF CRACKING HYDROCARBON'OILS Original FiledMay 21, 1927 INVENTOR m 0 k W d W m y TORNEYS operation from PatentedJuly 23, 1929.

EDWARD w. 'ISOM, OF SCARSDALE, NEW YORK,

COMPANY, OF NEW YORK, N. Y., A

ASSIGNOR TO SINCLAIR IIStEFININ'(ar CORPORATION OF MAINE.

ART OF CRACKING HYDROCARBON OILS Application filed Kay 21, 1927. SerialNo. 193,194. Renewed December 31, 1928.

This invention relates to improvements in the cracking of heavier andhigher boiling hydrocarbon oils, such as kerosene, gas oil, fuel oil orresidues, to produce lighter and lower boiling hydrocarbon oils such asgasoline or gasoline-containing cracked distillates, therefrom. Thisapplication 1s 1n part a continuation of my prior application filedAugust 28, 1922, Serial No. 584,111.

In carrying out the present invention, a body of oil to be crackedisma-intained at a cracking temperature, by circulating Oll from thisbody through heating tubes and backto the body and heating the oil to acracking temperature in the heating tubes, vapors are taken off fromthis body of 011 and subjected to a refluxing operation, refluxcondensate from this refluxing operation is forced once through aseparate heating conduit in which itis heated to a cracking temperature,and the hot oil products from this heating conduit are discharged intothe circulating oil on its way to the heating tubes first mentioned. Thehot oil products discharged from the separate heating conduit are thusforced through the first mentioned heating tubes in admixture with thecirculating body of oil. The injection of the hot oil products from theseparate heating conduit into the circulating oil may, with advantage,be used for effecting or promoting the circulation. Before the vaporsare subjected to the refluxing operation from which reflux condensate isreturned to this separate heating conduit, they may be subjected to another refluxing which reflux condensate is returned directly to the bodyof oil, heavier reflux condensate thus being returned to the body of oiland lighter reflux condensate supplied to the separate heating conduit.The oil forced through the separate heat ing ,conduit is advantageouslyheated to a higher cracking temperature therein than is the circulatingbody of oil. Relatively refractory stocks, such as reflux condensate orlighter reflux condensate, may thus be subjected to more severe crackingconditions in the heating conduit. Fresh oil may be supplied to thecirculating body of oil directly during the operation, and additionalfresh oil may be forcedv through the separate heating conduit togetherwith the reflux condensate supplied thereto In the treatment ofdifferent charging stocks some of which are relatively more refractorythan others, in carrying out the present invention, relatively lessrefractory stock is supplied directly to the circulating body of oil andrelatively more refractory stock is supplied to the separate heatingconduit. The operation may be carried out in a continuous manner bycontinuously discharging tar or piiftchl-laden, oil from the circulatingbody o 01 In one way of carrying out the invention, the crackingoperation carried out in the separate heating conduit is a vapor phasecracking operation In the separate heating conduit, in this method ofoperation, the oil is vaporized substantially completely and the vaporsare heated to a high cracking temperature The circulating body of oil ismaintained at a lower crac so that the temperature of the hot oilproducts from the'vapor phase cracking o eration is reduced astheyaredischarged into the body of. oil Undesirable reactions are thus arrestedand objectionable overt-racking usually incident to vapor phaseoperation may thus be avoided The 'oil supplied to the separate heatingconduit may thus be heated in vapor phase to a high cracking temperaturefor a relatively short time, the desired cracking effected and thecracked products then discharged into a body of oil where they arefurther subjected to the cracking conditions maintained therein beingforced to circulate first through the zone in which external heat isapplied to that body of oil but which cracking conditions are relativelymild. 7

e invention will be further described in connection with theaccompanyingdraw ings which illustrate, in a diagrammatic and conventional manner,in elevation and partly in section, an apparatus adapted for thepractice of the process of the invention, but it is intended and will beunderstood that this further description and illustration are for thepurpose of exemplification iand that the invention is not limited there-Referring to the drawings, 4 is maintained in the shell This oil iscirculated in a closed circuit from the shell or drum through thebattery of heating tubes 5 and back to the shelltor drum by means of thecirculating connections 8, 9 and 10. These circulating connections may abody of oil or drum 55 mg temperature oil, particularly 1 of heaviercomponents thereof, the shell or drum 55 is maintained undersuperatmospheric pressure. Vapors are taken off from the shell or drumthrough connection 11, passed through reflux condenser 12, vaporsremaining uncondensed therein passed to the reflux condenser 16 throughconnection 15, and vapors'remaining uncondensed in reflux condenser 16passed to a condenser (not shown) in whlch the cracked product iscondensed through connection 17. The final'condenser may be of anyordinary construction, and is connected to a receiver of ordinaryconstruction adapted to provide for separation of uncondensed vapors andgases from the condensed product. The pressure on the vapors may bereduced and'regulated by a valve 72 in connection 11 or by valve 73 inconnection 17 or by suitable valves arranged beyond the condenser orreceiver. Superatmospheric pressure may thus be maintained in the shellor drum .and the reflux condensers 12 and 16 may thus be. operated atthe same superatmospheric pressure or substantially at atmosphericpressure or atan intermediate pressure. Similarly, the pressure in thesystem 'may be maintained through the final condenser, or the final condenser may be operated substantially at atmospheric pressure or at anintermediate pressure.

The cooling and the refluxing of the va pors passing through the refluxcondensers 12 and 16 may be promoted or effected by passing fresh oil tobe supplied to the operation in indirect heat exchanging relationtherewith, for example, or this cooling and refluxing may be effected bysome extraneous cooling medium. In one advantageous method of operation,fresh oil, particularly less refractory fresh oil, supplied from tank 34through connection 36 including meter 37 by means of a pump 35 is passedfirstin indirect heat exchanging relation with the vapors in the secondrefluxing operation, then, through connection 39, in indirect heatexchanging relation with the vapors in the first refluxing operation,and then, through connection 40', introduced into the circulating bodyof oil. A check valve 41 is provided to prevent reverse flow throughconnection 40 and a valve 42 is provided for controlling the operation.Reflux condensate from the first refluxing operation, that carried outin reflux condenser 12, is

discharged through connection 13, and in densate again through theheating tubes 5 before it is again permitted to escape from the shell ordrum 55 as vapors. Part ofthe reflux condensate from reflux condenser12' may be discharged to the tank 19. Valves 74 and 75 are provided fordirecting the flow of this reflux condensate and for controlling theoperation in this respect. Reflux condensate from the second refluxingoperation, that carried out in reflux condenser 16, is discharged to thetank 19 through connection 18. The lighter reflux condensate collectingin tank 19 if returned to the circulating body of oil 4, tends tovaporize therefrom without substantial cracking thus utilizing heat forvaporization of these components which in the pres ent invention is madeavailable, at least in large part, for useful cracking of the oil. Atthe same time, the present invention provides an advantageous method forfurther treatment and cracking of this more refractory refluxcondensate.

This reflux condensate is forced from the tank 19, through connections20, 49 and 22, by means of pump 21, once through the heatlng conduit 23.This separate heating conduit is arranged in a furnace 24 in which hotproducts of combustion from the burner 29 pass over the heating tubesmaking up the heating conduit, the waste heating gases escaping throughstack flue 30. To assist in maintaining uniform furnace conditions, apart of the heating gases may be recirculatedcfrom near'the stack flueand admixed with the fresh hot products of combustion passing over theheating conduit. A return flue for this purpose is shown at 31. Thisreturn flue may be provided with a steam injector, as illustrated, orwith other suitable forcing means for eflecting recirculation of part ofthe heating gases. The hot oil products from the heating conduit-23 passthrough connections 25 and 27 to the injector nozzle 28 through whichthey are discharged into the oil circulating through connections 8 and 9from the shell or drum 55 to the lower ends of the heating tubes 5. herethe cracking operation in the heating conduit 23 is carried out in thevapor phase, a tar separator 26 is with advantage included in thedischarge connections. A check valve 32 to prevent reverse flow and avalve 33 for regulating and controlling the operation are also providedin the discharge cono nections from the heating conduit. Where acirculating pump is employed at 7,, for maintaining circulation from andback to the shell or drum 55 through the heating tubes 5, the pressureat the discharge end of the heating conduit 23 may be maintained at avalue just sufficient to force the hot oil products therefrom into thecirculating body of oil, or a higher pressure may be maintained in theseparate heating conduit. here a higher pressure is maintained in theheating conduit 23, this pressure may be reduced and regulated by meansof the valve 33. By employing a higher pressure in the heating conduit23, and introducing the hot oil products therefrom into the circulatingbody of oil so as to obtain an injector effect, this circulation can bepromoted, or the circulating pump 7 may be omitted and'this circulation.effected mainly by such injector action. When the combined operation iscarried out in this way, sufiicient pressure should be maintained in theseparate heating conduit to insure the desired injector action when thehot oil products therefrom are discharged intothe circulating body ofoil. In addition to the reflux condensate from tank 19, additional freshoil, particularly more refractory fresh oil, may be forced through theheating conduit 23 in admixture with the reflux condensate by means ofpump 21. This additional fresh oil may be supplied from tank 44 throughconnection 45 including meter 46 and check valve 47 to prevent reverseflow. Valves 48 and 50 are provided for controlling the supply of refluxcondensate and such additional fresh oil to the pump 21. In place ofsuch a single pump, separate pumps may be employed for supplying freshoil and reflux condensate from tank 44 and tank 19 to the heatingconduit 23.

A connection for discharging tar, or pitch-laden oil. from the shell ordrum is shown at 67. The operation in the shell or drum 55 can becarried out in a continuous manner by continuously discharging tarthrough connection 6". At the end of an operation. the charge of oiltherein may be reduced to a heavy flux or residue and this flux orresidue pumped out when the operation is discontinued. Connection 51 isprovided for pumping out this partof the still system at the'end of anoperation.

In carrying out the present invention, stocks of different character aresubjected to cracking conditions of special advantage with reference tothe particular stock treated. The oil forced through the heating conduit23 is subjected to relatively more severe cracking conditions thereinthan 15 the circulating body of oil 4. In one way of carrying out theinvention, the oil forced through the heating conduit 23 is heated to ahigh cracking temperature in the vapor phase therein. .More refractorystocks are advantageously subjected to more severe cracking conditionsin theheating conduit 23 while less refractory stocks are advantageouslysubjectedto the less severe crackmg conditions to which the circulatingbody of oil is subjected. The body of oil 4 is heated in a particularlyadvantageous manner by circulation through the heating tubes 5 andinternally by the hot oil products discharged from the separate heatingconduit. By maintaining a relatively high pressure on the drum or shell55 refractory but which nevertheless are with advantage subjected torelatively high crackmg temperatures may be subjected to particularlyappropriate of the operation. Likewise, this invention provides for theadvantageous separation of heavy and intermediate components refluxedfrom the vapors taken off from the combined operation and for the returnof these separate reflux condensates to that part of the operation inwhich they are subjected to the most appropriate treatment. Lessrefractory products of the combined operation may be returned directlyto the circulating body of oil t while more refractory intermediatecomponents produced by the combined cracking operation or vaporized fromthe fresh oil are supplied to the heating conduit 23 where they aresubjected to relatively more severe cracking conditions. The hot oilproductsdischarged from the separate heating conduit, in carrying outthis invention, are discharged into and admixed with thejcirculatingbody of oil while in highly reactive condition and the resulting mixtureis immediately circulated through the zone,

the heating tubes 5, where the circulating body of oil is in its mostreactive condition. lln this respect particularly, the two heatingoperations are combined in a particularly advantageous manner.

For theproduction of gasoline or motor fuel components, to illustrate,the temperature of-the oil body 4: may be maintained in the neighborhoodof 750 to 800 F. and the temperature of the hot oil products as they aredischarged from the heating conduit 23 may be maintained in theneighborhood of 1,000 to L100 F. Gas oil, or heavy gas oil, or fuel oil,may be supplied directly to the body of oil 4. Light gas oil or keroseneorthe bottoms from the redistillation of cracked distillates for theseparation of gasoline components may be supplied, to the heatingconduit 23 together with the reflux condensate su plied thereto. Thereflux condensate from the first refluxing operation may be returneddirectly to the body of oil 4 where it is of a less refractory characteror this reflux condensate may be supplied to the heating conduit 23where it is of a more refractory character. The

stocks which are less treatment in this part heating of the tubes 5 isregulated to avoid excessive formation of pitch or carbon. Theconcentration of pitch in the body of oil 4 may also be regulated bydischarging pitch- .laden oil therefrom and regulating the rate at whichoil is'supplied thereto and at which such pitch-laden oil is discharged.The pressure in the shell or drum 55 may be maintained in theneighborhood of from 90 to "125 pounds per square inch, for example, orhigher pressures may be used. I? i I claim:

1. A method of cracking hydrocarbon oils, comprising maintaining a bodyof oil at a cracking temperature by circulating oil from saidvbodythrough heating tubes and back to said body and heating the oil to acracking temperature in said heating tubes, taking. off vapors from saidbody of oil and subjecting them to a refluxing operation, forcing refluxcondensate from said refluxing operation once' through a separateheating conduit and heating it therein to a cracking temperature, anddischarging hot oil products from said heating conduit into the oilcirculating from said body of oil to said heating tubes.

2. A method of cracking hydrocarbon oils, comprising maintaining a bodyof oil at a cracking temperature by circulating oil from said bodythrough heating tubes and back to said body and heating the oil to acracking temperature in said heating tubes, taking off vapors from saidbody of oil and subjecting them successively to a first and a secondrefluxing operation, returning reflux condensate from the firstrefluxing operation to said body of oil, forcing reflux condensate fromthe second refluxing operation once through a separate heating conduitand heating it therein to a cracking temperature, and discharging hotoil products from 'said heating conduit into the oil oil'- culating fromsaid body of oil to said heating tubes.

3. A method of cracking hydrocarbon oils, comprising maintaining a bodyof oil at a cracking temperature by circulating oil from said bodythrough heating tubes and back to said body and heating the oil to acracking temperature in said heating tubes,

taking off vapors from said body of oil and subjecting them to arefluxing operation,

forcing reflux condensate from said refluxing operation together withfresh oil once through a separate heating conduit and heating themixture therein to a cracking temperature, and discharging hot oilproducts from said heating conduit into the oil circulating from saidbody of oil to "said heating tubes.

4. A method of cracking hydrocarbon oils, comprising maintaining a bodyof oil at a cracking temperature by circulating oilfrom said bodythrough heating tubes and back to said body and heating the oil to acracking temperature in said heating tubes,

taking off vapors from said body of oil and subjecting them to arefluxing operation,

" EDWARD W. ISOM.

